.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
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.\" %%%LICENSE_END
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     386BSD man pages
.\" Modified Sat Jul 24 18:50:48 1993 by Rik Faith (faith@cs.unc.edu)
.\" Interchanged 'needle' and 'haystack'; added history, aeb, 980113.
.TH MEMMEM 3  2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
memmem \- locate a substring
.SH SYNOPSIS
.nf
.BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
.B #include <string.h>
.PP
.BI "void *memmem(const void *" haystack ", size_t " haystacklen ,
.BI "             const void *" needle ", size_t " needlelen  );
.fi
.SH DESCRIPTION
The
.BR memmem ()
function finds the start of the first occurrence
of the substring
.IR needle
of length
.I needlelen
in the memory
area
.I haystack
of length
.IR haystacklen .
.SH RETURN VALUE
The
.BR memmem ()
function returns a pointer to the beginning of the
substring, or NULL if the substring is not found.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR memmem ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
This function is not specified in POSIX.1,
but is present on a number of other systems.
.SH BUGS
.\" This function was broken in Linux libraries up to and including libc 5.0.9;
.\" there the
.\" .IR needle
.\" and
.\" .I haystack
.\" arguments were interchanged,
.\" and a pointer to the end of the first occurrence of
.\" .I needle
.\" was returned.
.\"
.\" Both old and new libc's have the bug that if
.\" .I needle
.\" is empty,
.\" .I haystack\-1
.\" (instead of
.\" .IR haystack )
.\" is returned.
In glibc 2.0, if
.I needle
is empty,
.BR memmem ()
returns a pointer to the last byte of
.IR haystack .
This is fixed in glibc 2.1.
.SH SEE ALSO
.BR bstring (3),
.BR strstr (3)
.SH COLOPHON
This page is part of release 5.13 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
